First, a background art on a suction filter will be described.
Among turbocompressors, a two-stage turbocompressor has been proposed as exemplarily and schematically shown in FIG. 1. More specifically, a first-stage compressor 1 is connected at its suction port 2 to a suction line 4 with a suction valve 3 midway thereof. The suction line 4 has, at its one end or on its suction side, a suction filter 5 with a filter element 6 for removal of foreign matter such as dust. The first-stage compressor 1 is connected at its discharge port 7 to a suction port 9 of a second-stage compressor 8 via a line 10 with an intercooler 11 which cools compressed air to be introduced into the second-stage compressor 8 for reduction of a volume thereof. The second-stage compressor 8 is connected at its discharge port 12 to a discharge line 13 with an aftercooler 14. The line 13 is branched downstream of the aftercooler 14 into a compressed air supply line 15 and a blowoff line 16. The discharge line 13 downstream of the branched point is provided with a pressure switch 17 which controls opening and closing of the suction valve 3 and of a blowoff valve 18 in the blowoff line 16 (See JP 8-121398A).
As disclosed in said JP 8-121398A, the suction filter 5 employed in the conventional turbocompressor comprises, as shown in FIG. 2, a casing 19 with a suction section 20, a discharge section 21 centrally of the casing 19 and communicated with the suction line 4, a large-diameter filter-element mount 22 having peripheral openings communicated with the discharge section 21 and a large-sized cylindrical filter element 6 fitted over the mount 22; air sucked through the suction section 20 opened on a portion of the casing 19 is introduced via the filter element 6 into the discharge section 21 and during such passage of the air the foreign matter such as the dust is removed from the air.
As illustrated, most of such conventional suction filters 5 have the single filter element 6 for the single discharge section 21. Therefore, when replacement of the filter element 6 becomes required during an operation of the compressor due to, for example, clogging of the element, no problem will occur provided that the operation of the compressor can be stopped; however, there may be some cases where the single filter element 6 has to be replaced without stoppage of the operation of the compressor; then, removal of the single filter element 6 for replacement with another one will inevitably bring about no sealing or covering of the opening on the filter-element mount 22 due to the removal of the filter element 6 since suction of air must be continued. As a result, a lot of air is sucked through the uncovered opening on the filter-element mount 22 and there may be a fear that a lot of foreign matter such as dust to be removed by the filter element 6 is sucked without filtering during the replacement work of the filter element. Furthermore, replacement of the filter element requires much time and manpower since the filter element 6 is so large as to be handled by a crane and is hard to be treated.
Accordingly, an object of the invention is to reduce or remove the risk of a lot of foreign matter being sucked even at a replacement work of the filter element during the operation of the compressor and to conduct the replacement work readily and in a small amount of time.
Next, a background art relating to a turbocompressor and a method for compact assembling of the same will be described.
As a turbocompressor used for preparation of compressed air to be supplied to a demand such as a plant, there have been known two- and three-stage turbocompressors depending upon compressed air pressure requirement.
The two-stage turbocompressor is constructed such that it has first- and second-stage compressors with a rotary shaft rotated via a mechanism for speeding up a drive force from a motor to rotate impellers in compressing sections. Air sucked through a suction filter is compressed by the first-stage compressor and is discharged via a discharge port of the first-stage compressor into an intercooler which is an air cooler. Then, the compressed air from an outlet of the intercooler is introduced into the second-stage compressor so as to be compressed. The air thus compressed in the second-stage compressor is introduced into an aftercooler which is an air cooler, and is supplied via an outlet of the aftercooler to the demand. During the supply to the demand being stopped, the air is blown off from the aftercooler via a blowoff pipe, a blowoff silencer being arranged downstream in the blowoff pipe.
The three-stage turbocompressor is constructed such that provided are two or first and second intercoolers and a third-stage compressor. Air sucked through a suction filter is compressed by a first-stage compressor and is discharged via a discharge port of the first-stage compressor into the first intercooler. The compressed air discharged via an outlet of said first intercooler is introduced into the second-stage compressor so as to be compressed. The air thus compressed by the second-stage compressor is introduced into the second intercooler and is thereafter introduced from said second intercooler into the third-stage compressor so as to be further compressed. The air thus compressed by the third-stage compressor is introduced into the aftercooler and is supplied via an outlet of the aftercooler to the demand. During the supply of the compressed air to the demand being stopped, the compressed air is blown off from the aftercooler via the blowoff pipe, noise deadening being effected by a blowoff silencer at a downstream end of the blowoff pipe so as to prevent the noise from being generated during blowoff.
In such two- or three-stage turbocompressor, conventionally the blowoff silencer at the downstream end of the blowoff pipe is not mounted on the compressor but is arranged separately to be connected to the blowoff pipe; in this case, the silencer itself is made longer to increase an amount of sound absorbed. On the compressor, a simple muffler is mounted.
The blowoff silencer not mounted on the compressor but arranged separately in the two-stage turbocompressor has been proposed (See, for example, JP 2001-289168A).
The two-stage turbocompressor has been known in which integrally fabricated by casting are compressing sections of the first- and second-stage compressors, a receptacle for a power transmission mechanism which transmits a drive force for compressing operations of the compressing sections, a cooler casing for two air coolers, compressed air passages connecting the first- and second-stage compressors to the air coolers, respectively, the two air coolers being housed in said cooler casing in a partitioned manner (See, for example, JP 8-93685A and JP 10-252681A).
In the three-stage compressor, as schematically shown in FIG. 3, first-, second- and third-stage compressors 31, 32 and 33 are arranged; a discharge port of the first-stage compressor 31 and a first intercooler 34 are interconnected by a compressed air passage 37 so as to be integrally structured; an outlet of the first intercooler 34 and a suction port of the second-stage compressor 32 are interconnected by a compressed air passage 38 so as to be integrally structured; the second-stage compressor 32 and a second intercooler 35 are interconnected by a compressed air passage 39 so as to be integrally structured; and an outlet of the second intercooler 35 and an suction port of the third-stage compressor 33 are interconnected by a compressed air passage 40 so as to be integrally structured. The third-stage compressor 33 is connected via a compressed air passage 41 to an aftercooler 36. In such structure, integrally fabricated by casting into an integral cast casing in the same manner as in the two-stage compressor mentioned above are compressing sections of the respective stage compressors 31, 32 and 33, a receptacle for a power transmission mechanism which transmits a drive force for compressing operations of the respective compressing sections, a receptacle for two intercoolers 34 and 35 and compressed air passages 37, 38, 39 and 40 sequentially interconnecting the first-stage compressor 31, the first intercooler 34, the second-stage compressor 32 and the second intercooler 35. Only the two intercoolers 34 and 35 are incorporated in the integral cast casing; separately arranged is the aftercooler 36 to which the discharge port of the third stage compressor 33 is connected via an extension of the compressed air passage 41.
The blowoff silencer not mounted on the compressor but arranged separately as shown in JP 2001-289168A has problems that constructing the blowoff pipe is much troublesome and that space for installing the silencer must be ensured. On the other hand, in a case where the blowoff silencer is mounted on the compressor, no problem will occur if sufficient space for installation of the silencer is secured; however, if the place cannot be secured for the reason of, for example, space saving of the compressor, the silencer itself has to be made compact and simple, resulting in insufficient noise deadening.
In the two-stage turbocompressor in the form of integral cast casting as shown in JP 8-93685A and JP 10-252681A, the compressing sections of the compressors and the compressed air passages are integrally fabricated, so that the two-stage turbocompressor is applicable only for two-stage compression; similarly, a three-stage turbocompressor is applicable only for three-stage compression. Accordingly, the three-stage compressor cannot be used for, for example, one or two-stage compression and therefore cannot cope with special use.
Furthermore, though the two-stage turbocompressor may be in the form of integral cast casing with two air coolers being incorporate therein as shown in JP 8-93685A and JP 10-252681A, there has been no three-stage turbocompressor with three air coolers being incorporated in an integral cast casing; in fact, generally only two intercoolers are incorporated in the integral cast casing and the aftercooler is arranged separately or placed centrally.
Accordingly, there are problems that the number of the parts is increased and that the structure is made larger due to increase of installation area caused by such separate arrangement; the air pipe for connecting the third-stage compressor with the aftercooler must be extended, which leads to increase in pressure loss and thus deterioration in performance. JP 8-93685A and JP 10-252681A do not show three coolers incorporated in a casing in a three-stage turbocompressor at all.
Thus, an object of the invention is to provide a turbocompressor which can achieve space saving with respect to installation of a blowoff silencer so as to enhance noise deadening effect and which may be a three-stage turbocompressor compact in size and easily cope with one or two-stage compression.